Method of and apparatus for making cold cathode fluorescent lamps or the like



Dec. 25, 1945. c. HERZOG 2,391,573

METHOD OF AND APPARATUS FOR MAKING COLD CATHODE 'FLUORESCENT LAMPS ORTHE LIKE Filed MaFoh '7, 1944 2 Sheets-SheeI 1 INVENToR. /5 E0419419519205,

` A fran/wey Dec. 25, 1945. C HERZOG METHOD oF AND APPARATUS FOR MAKINGCOLD CATHoDE FLUoREscENT LAMPS 0R THE LIKE 2 Sheets-Sheet 2 Filed March7. 1944 Patented Dec. 25, 1'9'45 l METHOD oF AND APPARATUS Fon mime. comcA'rnoDE FLUonEscENT LAMPS on THE @a1-ll Herzog, Belleville, N. J.

Application March 7, .1944, serial No. 525,446

l1 Claims.

My invention relates to a mewthod of and apparatus for producingelectronic devices, such as gaseous discharge tubes including coldcathode uorescent lamps, neon lamps, radio tubes or the like', and tosuch devices.

An important object of the invention is to pro- (Cl. 316i-11) Figure isa perspective view, parts broken away. showing a modified manner oimounting the cathoder upon the contact extension of the retainer, i

videa continuouscmethod for performing the various steps in 'producingthe iinished product,

such as a cold cathode fluorescent lamp, and will reduce themanipulation of the tube to the minimum.

A further object 'of the linvention is-to provide a method of' the abovementioned character which will eliminate the baking of the coating ofthe tube in o, furnace as a, separate method.

A further object of the invention is to provide a method whichwillevacuate the tube and seal in the electrode at the same-time.

A further object of the invention is to provide a methodwhich willImaterially reduce the cost of baking cold cathode iiuorescent lamps.

, Figure 11 is a similar view showing a further modied'manner ofmounting the cathode upon the retainer,

Figure 12 is a similar view showing/ a further modified manner ofmounting the cathode upon the retainer, and

Figure 13 is a central vertical section, upon an enlarged scale, throughthe tube at the point of fusing the tube to the retainer, parts broken laway.

In the drawings, wherein for the purpose of,il lustration is shown a.preferred embodiment of my invention, the numeral l0 designates a glasstu-be, constituting the envelope of the cold cathode fluorescent lamp.'I'his tube may be of any suit-'- A further object of the invention istoprovide apparatus for use in the practice of the method. A furtherobject of the invention is to so mount the tubular electrode shell uponthe contact extension of the retainer or retainer for reducing heattransfer from the electrode shell Other objects and advantages of theinvention will be apparent 'during the course of the followingdescription.'

in the accompanying drawings, forming a part of this application and inwhich like numerals are employed -to designate lilre parts throughoutthe same.

Figure 1 is a central vertical longitudinal section through apparatusembodying my invention,

showing the baking steps, v

Figure 2 is a similar view through the tube, partly' diagrammatic,showing the vacuum baklng, "l

Figure 3 is a similar view showing sealing the bottom end of the tube,

Figure 4 is a, similar view showing cutting o the" bottom end of thetube, 'l

Figure 5 is a similar view showing gas insertion into the tube,

Figure 6 is a similar view showing mercury insertion into the tube,

Figure 7 is a similar view showing sealing the ktop end of the tube,

Figure 8 is a similar view showing cutting off the top end of the tube-and producing the finished product,

Figure 91s an enlarged central longitudinal sction through the completedlamp,

able diameter and length. These tubes are frequently a half inch indiameter and eight feet long, although the dimensions may be varied. Theinner surface of the tube i0 is covered or coated with a coatingcomposition containing a linely divided luminescent or iiuorescentmaterial, and this coating is dried. 1 may empioy the coatingcomposition disclosed in the patent to T. M. Cortese, 2,318,060, andthis coating may .tbe applied and dried in accordance with the methoddisclosed in the Cortese patent. However, the coating is not baked in aseparate oven, but the baking occurs as a step in my method. The tubei0, Figure 1, has the coating compositiom il, which may be thefluorescent coating composition disclosed in the Cortese patent, ex-

tending originally throughout its entirelength, and dried but not baked,and this dried coating is removed from the ends of the tube I0 to points'f i2, leaving cl'ean or 'uncoated zonesi3 and I4.

The tube I0 with the dried interior coating ll is vertically arrangedwith its opposite ends open and held within a holder I5 to be supportedthereby. -4

-Disposed within the opposite ends of the tube l0 are electrodes,including electrode shells I 6. Each electrode shell is made of thepurest iron obtainable. and the interior of the shell is coated with anelectron emitting material, as is well known. Each electrode shell ispress fitted into a cup-shaped contact extension I1 of a retainer i8,surrounding the electrode shell and spaced therefrom. The retainer I8has a larger diameter than the electrode shell I6 and has a smallerdiameter than the tube I0, and the ltube is fused to the retainer, toprovide a vacuum-tight joint,

7,) sleeve 30.#

'ment therewith, to shift 'I'his cap is provided with as will beexplained. The retainer forms a. ring or band extending radially beyondthe electrode port is connected with a pipe shell I8. It desired, theelectrode shell I6 may be welded to the contactextension' I1. Theretainer I8 is made of a special commercial chromeiron alloy which hasthe same expansion coel- /cient as glass. The retainer I8 and thecontact extension I'I have their ends imperforate, as

shown.

I also contemplate usingthe form of electrode which is an integral unit,as shown in Figure 2l of my copendlng application for Method oi andapparatus for producing cold cathode fluorescent lamps and to suchlamps. led January 26, 1944, Serial No. 519,666.

I may employ the` lelectrode shown in Figure l0. In this ligure, I is anelectrode shell, identical with the shell i8 and having a closed endIl',

f which is welded to a wire I8'. This wire is welded to the end of thecontact extension I1 of the retainer I8. The wire I8' supports theelectrode shell I8' in spaced concentric relation to the contactextension I'I and the retainer I9.

In Figure 11, I have shown a slightly diflerent arrangement whereinwires I9' are welded to the sides of the electrode shell I6' and to the4bottom of the retainer I8. The arrangement is otherwise identical.'

In Figure 12, I have shown a further similar arrangement, wherein aradialribbon or strap is welded to the end I1' of the electrode shelland extends outwardly beyond the same and is welded to the bottom of theretainer I8. The arl rangement is otherwise identical with that shown inFigure 10.

e The advantage of the electrode shown in Figures 10, 11` and 12. isthat the electrode shell is spaced from the contact extension Il andretainer I8 and connected therewith by the wire or wires or ribbon andis transmitted by conduction from -'the shell I6' to the contactextension or retainer I8 is reduced. This is advantageous after made andis operating in use.

'I'he electrode shell I6' corresponds to the electrode shell IB and thesame retainer and contact extension is used.

I will now describe the operating units of apparaltus which is used inthe practice of the method. The operating units generally by thenumerals I9 and 28. Each operating unit includes sin outer block 2l,having a reduced inner end 22, which is screw-threaded, and providedwith a main vertical chamber 23. This main vertical chamber receivescompressible packing 24, which may be rubber, asbestos, or s. mixture ofthe same, or anyother suitable mate rial for enacting a vacuum-tightjoint with'the glass tube I8. A follower ring is movable into thechamber 23 to compressthe packing 24. `Ihe chamber 23 leads into achamber 26. Each block is provided with a vertical opening 21 to receivethe shank 28 of a, clamp or socket 29. Thissocket 29 may be resilient.The shank 28 is electrically insulated upon the block 2l by aninsulating The'shanks 28 are connected with the apposite poles of asource of current by lead wires 32, for a purpose to be screw-threadedextension 22 has a cap 33 mounti ed thereon and having screw-threadedengagethe followerring'25 and compress the packing.

s. water space or, jacket 34, and the coolant may enter at the pipe andleave by the pipe 38'. The unit 28 is provided with a hot air the amountof heat which.

the lamp has' been 'l are designated.

311, ieaalng inte the chamber as and this het m- 38, having a cut-oi!valve 39 connected therein. The

v to a, source of hot air and the-hot air is supplied described. Eachreduced supplied to the glass tube has a temperature of port 74' throughthe pipe 38 so that it may enter the glass tube I8 at substantially 400C. 'I'he unit 20 also has a vacuum port`40. in communication with thechamber 26 and connected with a pipe 4 I, having a cut-off valve 42connected therein. The pipe 4i is connected with a source of vacuum. f

'Iihe unit I9 has a tube 43, connected therewith, and this tubecommunicates with a-port 44, leading into the chamber 28. The tube 43has a hotl air discharge tube 45 and a gas inlet tube 46, connectedtherewith.` A rotary valve 41 is arranged at the union o! the tubes 43,45 and 46, and may be manipulated to place tube 43 in communication withtube 45, or tube 43 in communication with tube 46, or to cover the boreof the tube' 43 or tube 46.

The unit I9 is provided in its upper end with a well 48 for holdingmercury and has a tapered recess 49 beneath the well to receive atapered rotary valve element 50. This valve element is turned by a vstem5l having a crank 52 and is urged upon its seat by a spring 53. Thevalve element 58 has diametrically oppositely arranged pockets 54,` forreceiving measured amounts of the mercury and discharging the same intoan inclined port 55, leading into the chamber 29. The well 48 is incommunication with a vertical port 56 having a. horizontal branch 51which leads into the recess 49 and feeds the mercury into the pocket 54.The vertical port discharges at its lower end into a horizontal recess51', arranged beneath the valve element 58. It is thus seen that themercury contacts with the upper and lower ends of the valve'element 50and seals these ends, whereby a vacuum-tight joint is elected.

The practice of the method is as follows:

I take the glass tube I0 having the dried un baked fluorescent coatingyIl and its ends open,y and insert the same in the holder I5, Figure l,which vertically supports the tube. The 'electrode shells I6 are held bythe socketsor clamps 29 by inserting the contact extensions I'I intothese sockets. The socket or clamp 29 has a smaller diameter than theretainer I8, as clearly shown in Figure 13. The units I9 and 28 are nowbrought into proximity to the opposite ends o! the tubes I9 and theelectrode shells I6 are inserted into such opposite ends. 'I'he sockets29 retain the electrode shells in spaced concentric relation to thetubev I8. The ends of the tube I0 are passed into the packing 24 withinthe chambers 23. The units I9 and 28 may be supported by any suitablemeans. The caps' 33 are now screwed up so that the follower rings 25place the packing under compression and form vacuum-tight joints Iwiththe tube I0. The coolant is properly circulated through the caps 33. Thevalve element 58 may now be in the position shown in Flgure 1, wherebythe inner pocket 54 is empty |while the outer pocket 54 is lled with themercury. The valve element 4l may now be inthe position shown in Figurel, whereby the port 44 is in communication with the hot air dischargeport 45, while the port 48 is covered. The valve element 42 now coversport `40, while valve element 39 is open. Hot air is nowsupplied-through the pipe 38 and circulates through the glass tube l0and discharges from the glass ltube through the pipe 45. This hot airthus substantially 400 C. This hot air bakes the dried iluorescentcoating II in whole or' in part. The

pipe 38 leads baking.

plied to the top hl heated by the action of.

mg y the shell i3 and retainer plas.

with the hot air through' the pipe 45. It is advantageous to bake thecoating in this manner, as the tubes are long and require a largefurnace for The bakingy in accordance with my method does not plasticizethe tube.

After the baking operation, Figure 2, the valve 39 is closed and valve41 turned to cover Dort 44,

and valve 42 turned to the open position. The

interior of the glass tube l is no'w placed in communication with asource of vacuum and is suitably evacuated. During this evacuation, theelectrode shells I 6 are connected with the opposite poles of the sourceof current, through the wires 82. This is done to heat the electrodeshells` I6 and drive on undesirable gases and impurities. When theelectrode shells I6 are thus connected with the opposite pole of thesource of current, of a suitable character; they become highly heatedand the tube l@ is heated, which aids in baking the coating H. Thisheating action of the electrode shells l5 is continued for a suitablelength of time, indicatedby a small piece of paper contacting with theheated. tube 'l u becoming browned or partly charred. When this occurs,the electrode shells i6 are disconnected from the source oi current.

lAfter this and when the proper vacuum is at tained within the tube lE), Figure 3, the valve d2 is turned to cover the'port Il@ and hold thevacuum within the tube. Before the tube has materially cooled, a highfrequency coil A is brought intoav position for surrounding the lowerend of the tube and the lower electrode shell lo, and when the currentis turned on, the coil will heat the electrode shell I'B and retainer I8by induction. This electrode shell and retainer may be heated toy a highpoint and the heat radiating from the same vides a vacuum tight jointand the action may be aided by forming jaws if necessary.

The upper end 6| of the tube, Figure 8, is now` f severed by the bladesB2.

will heat the adjacent portion 5l ofthe tube, and

this portion 'i'will be plasticized and drawn inwardly by the action ofthe vacuum within the,

tube 9E. This portion 51 Will be then become fused Ato the retainer i8for forming a vacuumtight joint therewith. This action may be aided I bythe use of forming jaws, if necessary.

`The lower end 53 of the tube, Figure d, is now severed from the tube byknives 59. Theseknives will not engage the clamp 29 which has a smallerdiameter than the retainer i8, as shown in Fig ure 13. The valve i? isnow turned to place the tube d6 in communication with the port M,to-supply a small amount of inert gas, such as'argon or neoninto thetubeit, Figure 5. The amount of inert gas thus supplied issrnall and doesnot perceptibly change the degree or' vacuum in the tube. `The valve t1is nowl turned to to cover the port de.

By this time, the temperature of the tube l0 is materially reduced andmay be at approximately room temperature, Figure 6. The valve elementSi! is now turned to introduce the measured amount of mercury into theport 55 and this mercury drops to the bottom of the tube lll. Thismeasured amount of mercury is ordinarily a ball of slightly less thande" in diameter.

the neutral position The high frequency coil A, 'Figure 7, is now aitube it adjacent to the electrode shell is the coil and the of theupper'electrode shell it, and this the tube. which within the tube I8.yThis 91'0- port'ion 6u of the vacuum the retainer Figures 8 and 9 showthe complete lamp. The electrode shells I-6 arel arranged'within theopposite ends of the tube l0- and have their parts or retainers sealedtherein to provide vacuumltight joints. The retainers I8 hold ltheelectrode shells in spaced concentric relation to the tube I0. Thecontact extensions Il project outwardly beyond the ends of the tube IB,for engagement with the socket terminals, for supplying current to thelampl when in use.

When the electrodes embodying the cathode shells I6' and shown inFigures 10, 11 and 12, are used, the coil A heats principally theretainerl, which, in turn, heats and plasticizes thetube ill. All othersteps of the method remain identical with those shown and described.

It is to be understood that the apparatus herewith shown and describedis to be taken as a preferred embodiment of the same, and that variouschanges in the shape, size, and arrangementlof parts may be resorted to,and that changes may be resorted to in the orderl of the steps of themethod, and in the shape, size and arrangement of parts of. the cathodeunits, without departing from the spirit of my invention or the scope ofthe subjoined claims.

Having thus described my invention, I claim:

l. The method of making a coldcathode fluorescent lamp or the like,comprising supporting a glass tube having its opposite ends open and itsinner surfacecoated with an unbaked uorescent inert gas into the tube,introducing mercury into the tube, heating the other electrode byinduction and causing the same to heat and plasticize the adjacentportion of the tube and fusing such adjacent portion to the electrode,and cutting ou the outer adjacent portion of the tube.

2. The method of making a cold cathode nuorescent lamp or the like,comprising supporting a glass tube having its opposite ends open and itsinner surface coated with an unbaked fluorescent compound, introducingelectrodes into the tube near its ends and holding them generallyconcentric with relation to the tube, circulating hot air through thetube to bake the coating, evacuating the tube, connecting .theelectrodes with a source of current to heat them and the tube to aidinthe baking, heating the tube adjacent to one electrode to plasticize thesame. and fuse it to the electrode, cutting oi the outer adjacent end ofthe tube, introducing an inert gas into the tube, introducing mercuryinto'the' tube, heating the'tube adjacent tc rthe other electrode toplasticize the same and yfuseit to such electrode, and

cutting off the outer portion ofthe tube.

3,"The method of making a coldy cathode fluorescent lamp or` the like,comprising supporting a .glass tube having its opposite ends open andits inner surface coated with an unbaked uorescent compound, introducingelectrodes into the tube near its ends, the electrodes having retainersextending radially beyond the same, supporting the electrodes within thetube, circulating hot air through the tube to bake the coating,evacuating the tube, connecting lthe electrodes with a source of currentto heat them and the tube to aid in the baking, heating the tubeadjacent to one electrode to plasticize the same and fuse it to theretainer of such electrode, cutting off the outer end of the tubeadjacent to such retainer, introducing an inert gas into the tube,`introducing mercury into the tube, heating the tube adjacent to theptherelectrode to plasticize it and fuse the same'to the retainer of -suchelectrode, and cutting of! the outer portion of the tube adjacent to theretainer of the last named electrode.

4. The method of making a cold cathode fluo um-tight joint, iintroducingan inert gas into the Y open end of the tube, introducing mercury intothe open end of the tube, heating the tube adiarescent lamp or the like,comprising supporting a glass tube having its opposite end s open andits inner surface coated with a fluorescent compound, introducingelectrodes into the ends of the tube and supporting them near and spacedfrom such ends, evacuating the tube",l connecting the electrodes with asource of current during the evacuation, heating one electrode byinduction and caus- V ing the same to heat and plasticize the adjacentportion of the tube and fusing such adjacent por- 5. In the method ofmaking a cold cathode uo- I rescent lamp or the like, the steps ofsupporting a glass tube having its inner surface coated with afluorescent compound and having its ends open, introducing into the openends of the'tube electrodes having` radially enlarged bands, and concentto the other retainer toplasticize the tube and fusing the tube totheretainer for forming a vacuum-tight joint, the retainers holding theelectrodes spaced from the tube.

9. The method of making a cold cathode iiuorescent lamp or the like,comprising introducing into bodyv portions having chambers the open endsof a glass tube having its inner surface coated with an unbakedfluorescent compound,

- supporting within the' tube near itsends electrodes, introducing hotair into one chamber and circulating the same through the tube anddischarging the hot air from the tube into` the other such adjacentportion to the electrode, introducing an inert gas into the tube throughone chamber, introducing mercury into the tube through one chamber, andheating the other electrode by electrical induction and causing the sameto heat and `plasticize the adjacent portion of' the tube and fusingsuch adjacent portion to the electrode.

necting one open end of the tube' with a source v of vacuum to evacuatethe tube, heating the electrodes by electrical induction and causingthem to heat and plasticize adjacent portions of the tube and fusingsuch adjacent portions to the bands for providing vacuum-tight joints.

(j. In the method. of making a cold cathode fluorescent lamp or thelike, the steps of supporting a glass tube having its opposite ends openand its inner surface coated with a fluorescent compound, circulatinghot airthrough the tube to bake the compound, supporting electrodeswithin the tube near its ends, and heating the electrodes by electricalinduction and causing them to heat and plasticize the adjacent portionsof the tube for fusing the adjacent portions to the cathodes.

7.`In the method of making a cold cathode fluorescent lamp or the like,the steps of supportend of the tube, heating the metal band by elec- 10.In the method of making a cold cathode fluorescent lamp or the likeI thesteps of supporting a glass tube having one end open and its innersurface coated with a fluorescent compound, introducing into the openend of the glass tube a tubular electrode having a metal band extending.radially beyond the tubular electrode, evacuating the tube through theopen end of the tube, heating the metal band by electrical induction andcausing the metal band to heat and plasticize the adjacent portion of.the glass tube and fusing such adjacent portion of the glass tube to themetal band for providing a vacuum-tight joint, the metal band holding atubular electrode spaced from the glass tube.

11. In the method ofmaking a nuorescent lamp or the like, the steps ofsupporting a glass tube having one end open and its inner surface'coated with a fluorescent compound, introducing into the open end of theglass tube an electrode having a metal band extending radially beyondthe electrode, evacuating the tube through the open trical induction andcausing the'metal band to heat and plasticize the adjacent portion ofthe glass tube and fusing such adjacent portion of the glass tube to themetal band for providing a vacuum-tight joint, the metal band holdingthe electrode spaced from the glass tube.

' CARL mzoo.

